I wrote a guest post on Astrobites, about LIGO’s 2019 detection of a neutron star merger with a single detector:
Gravitational waves are ripples in space created by massive objects when they accelerate. That includes objects that orbit each other, and in the case of merging black holes or neutron stars the gravitational waves are big enough that we can detect them. In April 2019, the LIGO gravitational wave detector found its second binary neutron star (BNS) merger in an event dubbed GW190425 (the first was in August 2017). Unlike other LIGO and Virgo detections, GW190425 was definitively observed by just one detector rather than the usual two or three. The LIGO detector in Hanford, Washington, was offline for a couple of hours and missed the event, while the Virgo detector in Cascina, Italy, didn’t detect it strongly enough. That left just the LIGO detector in Livingston, Louisiana.